Rainier, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 41.6 °F (low) to 60.7 °F (high). Annual precipitation averages 50.1 Inches. Rainier is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 34.0 °F | 46.2 °F | 7.1 in. |
| February | 33.7 °F | 49.2 °F | 4.83 in. |
| March | 35.7 °F | 53.5 °F | 5.47 in. |
| April | 38.6 °F | 58.7 °F | 4.0 in. |
| May | 44.1 °F | 65.8 °F | 2.4 in. |
| June | 48.5 °F | 70.4 °F | 2.01 in. |
| July | 52.1 °F | 77.4 °F | 0.67 in. |
| August | 52.2 °F | 78.3 °F | 1.05 in. |
| September | 47.9 °F | 72.2 °F | 1.95 in. |
| October | 41.9 °F | 60.7 °F | 4.77 in. |
| November | 36.7 °F | 50.8 °F | 8.3 in. |
| December | 33.6 °F | 45.2 °F | 7.54 in. |
| Annual | 41.6 °F | 60.7 °F | 50.09 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 8b : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 8a : 10°F to 15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |